Medical device approaches

ABSTRACT

A system and method for providing image guidance for planning approach paths for one or more medical devices at a target location. The system can receive a volumetric medical image, determine a density of content within the volumetric medical image, receive an indication of a target location within the volumetric medical image, identify obstructing objects within the volumetric medical image, and determine a plurality of pathways from an approach region of the volumetric medical image to the target location. The system can cause a display to concurrently display the volumetric medical image and a plurality of emplacements for one or more medical imaging devices.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 15/199,711, filed Jun. 30, 2016, which claims the benefit of U.S. Provisional Application No. 62/195,676, filed Jul. 22, 2015, each of which is incorporated by reference herein in its entirety for all purposes. Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are incorporated by reference under 37 CFR 1.57 and made a part of this specification.

BACKGROUND

Image-guided surgery makes use of imaging to aid the surgeon to perform more effective or more accurate surgery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate exemplary volumetric medical images for image-guided medical procedures.

FIG. 2 illustrates a two-dimensional slice of a volumetric medical image with exemplary image scanning and needle approach paths.

FIG. 3 illustrates a three-dimensional volumetric medical image with exemplary image scanning and needle approach paths.

FIG. 4 is a flow diagram illustrative of an embodiment of a routine implemented by the system to display medical device emplacements.

FIG. 5A is a diagram illustrating an embodiment of an environment for medical device approaches.

FIG. 5B is a diagram illustrating an embodiment of a rendering of medical device approaches on a head mounted display.

DETAILED DESCRIPTION

Implementations disclosed herein provide systems, methods, and apparatus for guidance tasks related to pose and/or emplacement of medical devices. Certain embodiments pertain to systems for facilitating visualization of medical imaging device scanning approaches and/or needle approaches for surgical applications. Visualization of medical device poses and/or emplacements can allow a user to select a desirable needle insertion point to minimize insertion or repositioning attempts.

Systems and methods described herein can be used to determine one or more poses and/or emplacements of various medical devices. The term “emplacement” and the term “pose” as used herein are broad terms encompassing their plain and ordinary meanings and can refer to, without limitation, position, orientation, the combination of position and orientation, or any other appropriate location information.

As discussed elsewhere herein, there are numerous types of volumetric or 3D data that various embodiments of the guidance system herein can display. The term “volumetric medical image” is a broad term that encompasses its ordinary and customary meaning, and includes, without limitation any data in a volume or 3D space that can be displayed. The volumetric medical image can include, without limitation, one or more of a CT scan, an MRI, other 3D intraoperative or preoperative imaging data, other volume data, segmented internal organs, segmented blood vessels, annotations, tumors, etc. Such data can include CT scans, MRI, PET, 3D ultrasound, and any of numerous other types of 3D data. In some embodiments, in order to display 3D data on a 2D interface, such as a computer screen, or even a 3D interface, such as a head-mounted display or other 3D display, a subset of the data is chosen to display. This subset of data can include axis-aligned slices, the entire volume, or a sub-volume of the data. An inherent difficulty with image guidance is the display of three dimensions of data on a two-dimensional screen or “dual eye” three-dimensional display. When displaying 3D data, such as CT scans, a system might only display a single plane, or show three orthogonal planes separately on the screen. The data can also be shown as a volumetric ‘block’ of data, as shown in FIG. 3.

FIGS. 1A and 1B illustrate exemplary volumetric medical images 100 for image-guided medical procedures. The image 100 can be obtained based on any medical imaging technology as described herein, such as ultrasound, CT scan, MRI, open-magnet MRI, optical coherence tomography, positron emission tomography (“PET”) scans, fluoroscopy, ultrasound, or other preoperative, or intraoperative 2D or 3D anatomical imaging data. The image 100 can include multiple planes or slices 110 of image data. In some aspects, the volumetric medical image 100 can be obtained as a plurality of slices 110 from an imaging device configured to perform multiple 2D scans, or can be obtained as 3D volume data from an imaging device configured to generate 3D data. Where volumetric imagery is obtained from 2D scans, the planes or slices 110 can be the slices as obtained from the 2D scans, or they can be modified and/or generated to be, for example, parallel to the plane of a region of interest.

As depicted in FIG. 1B, a plane or slice 110 of the volumetric medical image 100 can include a cross-sectional view of a portion of a subject 120. In various embodiments, the location and orientation of the plane or slice 110 can be selected automatically based on detected structures within the volumetric medical image 100, or can be selected manually by a user. For example, the location and orientation can be selected so as to provide a cross-sectional view of a target structure 130, such as a lesion, tumor, or other structure.

In some embodiments, a region of interest 140 can be selected within a plane or slice 110. The region of interest 140 can be selected automatically or by a user, for example, based on a location of an emplacement sensor associated with a medical device (e.g., an ultrasound probe) manipulated by the user. In some implementations, the system can utilize and/or display imagery associated with the medical device (e.g., ultrasound image data obtained from an ultrasound probe) in addition to (e.g., superimposed upon) the volumetric image data. The data shown in the region of interest can be any appropriate visualizable medical data, not limited to ultrasound or CT data. Further, the data displayed outside of the region of interest can be any visualizable medical data, and can even be from the same data set as the data shown in the region of interest. For example, MRI data can be shown in fading planes outside of the region of interest and in focus (and visualizable through a tunnel) inside the region of interest. Further, annotation can be displayed along with the rendering of the visualizable medical data inside and/or outside of the region of interest. In this manner, a user can see the annotations in the context of the visualizable medical data.

In various embodiments, more than one set of visualizable medical data can be rendered. Each one can be rendered in a different manner. For example, they can be rendered with different transparencies, brightnesses, contrast, colors, etc. Further, one or more can be rendered with a different transparency, brightness, contrast or color as distance from the region of interest increases. For example, brightness can decrease and/or transparency can increase further from the region of interest 140.

FIG. 2 illustrates a 2D slice 200 of a volumetric medical image with exemplary image scanning and needle approach paths as determined by a guidance system. The exemplary slice 200 depicted in FIG. 2 includes a cross-sectional image of a torso of a patient, including sections of skin 202, bone 204, gas 206, and other internal tissues 208, as well as a target structure 210 (non-limiting examples: a lesion, tumor, or other target). Also depicted are a suggested scanning path 212 for an ultrasound probe and suggested approach paths 216 for a needle 218 or other invasive medical device.

The target structures 210 can be identified in a variety of ways. In some embodiments, the guidance system can allow a user to mark a target by interacting with the display of the volumetric medical image. For example, consider a procedure where the doctor is using the guidance system with an ablation needle 218 and an ultrasound probe 214. The doctor can mark the target structure 210 by pressing a button on a keyboard or mouse, touching a screen, pointing with a medical device, gesturing or issuing a verbal command, or with any other appropriate method, as described in greater detail in U.S. application Ser. No. 14/166,179, entitled, SYSTEMS, METHODS, APPARATUSES, AND COMPUTER-READABLE MEDIA FOR IMAGE MANAGEMENT IN IMAGE-GUIDED MEDICAL PROCEDURES, and Ser. No. 13/014,596, entitled, IMAGE ANNOTATION IN IMAGE-GUIDED MEDICAL PROCEDURES, each of which is incorporated herein by reference in its entirety.

In some embodiments, the system can detect the target structure 210 within an image stream obtained from an imaging device manipulated by the user (e.g., an ultrasound probe 214). In certain embodiments, the location of the target structure 210 can be marked at the point where a needle 218 intersects with the ultrasound image plane, where the needle's projection intersects with the ultrasound image plane, or any other appropriate relationship (such as at the location of the tip of the needle). For example, when a physician identifies a target structure 210 within the ultrasound image, she can point to it using the needle 218 even if the needle 218 is outside the body of the patient. The physician (or assistant) can press, for example, a button or foot pedal, which informs the image guidance system to store the 3D position of this target structure 210. In some embodiments, the target structure 210 can be identified based at least in part on the amount of time the physician spends observing an object or the amount of time that a medical device, or corresponding emplacement sensor, is located at a particular emplacement. For example, if a lesion or other abnormal structure is detected within the ultrasound image, and the physician keeps the probe 214 in the same location for a threshold time period (e.g., 3 seconds, 5 seconds, 10 seconds, 15 seconds, or longer), the guidance system can determine that the object is a target structure 210 and store its location.

In certain embodiments, the system can identify multiple target structures 210. For example, physicians, during some liver ablation procedures or other procedures, can manage fifteen target structures 210, or even more. The guidance system can store and display any number of target structures 210 concurrently. If there is more than one target structure 210 in view, the image guidance system can display a number or other indicator next to each one (not pictured). In some embodiments, in order to reduce visual clutter if there are many target structures 210, those target structures 210 which are closer to the ultrasound image plane can be drawn more saliently or vividly (with more bold color and thicker lines) while the points that are far away are drawn less saliently (more transparent, blurred, muted colors, etc.).

In addition, to identifying a target structure, the system can analyze the various types of tissue within the medical image to determine an approach path for the medical device. For example, ultrasound waves emitted by an ultrasound probe 214 may be able to travel through soft tissues 208 of a patient, but can be blocked or scattered by denser tissues such as bone 204, or by regions of lower density, such as gas 208. An ablation needle 218 may be able to travel through soft tissues 208 and/or regions of gas 208, but may be unable to travel through bone 204. In addition, needle approach paths can be chosen so as to avoid critical or delicate regions such as blood vessels or vital organs (not shown), even though such regions do not present an obstacle to ultrasound scanning.

Thus, when a 2D slice 200 is obtained, the guidance system can analyze the image to determine the tissue type or density of various regions of the image. In some embodiments, the guidance system can analyze the slice 200 based on an intensity of some or all pixels or voxels within the slice 200. The system can determine a radiodensity or intensity of voxels based on the Hounsfield unit (HU) scale or other suitable scale. For example, an intensity of greater than 700 HU can indicate bone, while an intensity of between −1000 HU and −350 HU can indicate intestinal gas. However, it will be understood that different imaging devices can output different HU for different types of tissue or can use different scales for intensity of voxels.

In some embodiments, the system can analyze the intensity level for each voxel of the medical image to determine the tissue type and/or object density. In certain embodiments, the system can use edge detection to identify objects, for example, to identify the location of skin 202 within the image slice 200. In some aspects, the system can use known HU values of critical or delicate regions (e.g., large blood vessels, heart, etc.) to identify the critical or delicate regions. Furthermore, in certain embodiments, such as with medical images involving the chest or abdomen of a patient, the system can analyze one or more image slices 200 taken at different parts of the breathing cycle. In this way, the system can determine the emplacement of the objects within the image slices at different parts of the breathing cycle and to identify deformations of the objects caused by breathing. It will be understood that the system can use other scales or measurements to identify the objects in the medical image, such as, but not limited to, manual or automatic segmentation, annotation, as described in greater detail in U.S. application Ser. No. 13/014,596, entitled, IMAGE ANNOTATION IN IMAGE-GUIDED MEDICAL PROCEDURES, previously incorporated herein by reference, etc.

In addition to analyzing the content of the medical image, the system can determine one or more medical device approach paths 216 to the target structure 210 from an approach region. The approach region can correspond to a surface or perimeter of the medical image and/or a desired start point, surface, or perimeter within the medical image. For example, the system can determine and display paths to the target structure from the surface of the medical image and/or from a particular structure within the medical image, such as the skin, an intestine, etc. In certain embodiments, to identify medical device approach paths 216 to the target structure 210, the system can analyze a plurality of paths between the target structure 210 and the approach region of the medical image.

In some cases, the system can use ray tracing or ray casting to identify paths to the target structure from the approach region of the image. For example, the system can analyze voxels along a particular path to identify paths between the target structure 210 and the approach region.

In some embodiments, the system can use one or more rendered images to identify paths to the target structure. For example, the system can render one more images from the perspective of the target to the approach region. In some embodiments, the system can treat the target as a point-of-view location and capture the voxels located between the target and the approach region, similar to a camera taking a picture. In certain embodiments, the volume of the captured voxels can generally correspond to a trapezoid, cone, frustum, or other shape.

In certain embodiments, the one or more images can be from different angles with respect to the target. As a non-limiting example, if the approach region is the surface of the 3D volume and the target is located within the 3D volume, the system can render six images (each one from the perspective of a different side of a cube corresponding to the target). It will be understood that fewer or more images can be rendered from different perspectives, as desired.

The system can render the captured images (or captured voxels). As part of the rendering process, the system can map the captured volume of voxels or imaged volume to an image area or region. In addition, the system can identify how to treat the different voxels during the rendering process. For example, the system can average the voxels that are to be located on a point of the image area, use the minimum or maximum voxel for the point of the image area, etc. In certain embodiments, the system can identify voxels that do not satisfy a density threshold (or otherwise not to be used for a medical device approach), as described in greater detail below, to be rendered differently than voxels that satisfy the density threshold. For example, if any one of the voxels that are to be mapped to a location in the image area do not satisfy the density threshold, the system can color code the location, such as by whiting or blacking it out, etc.

The one or more rendered images can be applied or mapped to the approach region of the 3D volume for viewing. With continued reference to the example, the system can map the one or more images to the surface of the 3D volume. Accordingly, a user can view the images on the approach region. In some embodiments, the system can also analyze the rendered images (non-limiting examples: using voxel intensities, edge detection, etc.) to identify locations in the rendered image in which the approach region is visible. The identification of the approach region within the image can indicate a direct path between the approach region and the target structure 210.

In certain embodiments, the system can analyze the image slice 200 along a series of circular paths of increasing or decreasing radius and centered on the target structure 210 (e.g., from the target structure 210 outward, or from the approach region). For example, the system can analyze the voxels within a sphere and then expand the sphere and analyze voxels within the expanded sphere. Analyzing a series of circular paths can be efficient, as angular segments of a circle that are deemed unacceptable for an approach path (e.g., due to the presence of bone) can be eliminated and the same angular regions can be omitted from the analysis of later circular paths, reducing processing time.

In analyzing the various paths between the target structure 210 to the approach region, the system can apply one or more criteria to identify one or more medical device approaches 216. For example, the system can use a density threshold, characteristics of a medical device, such as length, width, thickness, diameter, scan length, scan width, number transducer crystals, etc., to identify one or more medical device approaches.

In certain cases, the system can use characteristics of the medical device to determine the medical device approach. The medical device can be an invasive medical device, such as, but not limited to, biopsy needles, ablation needles, surgical needles, nerve-block needles, or other needles, electrocautery device, catheters, stents, laparoscopes or laparoscopic cameras, ultrasound transducers, or other instruments that enter a part of the body, or a non-invasive medical device that does not enter the body, such as, but not limited to, ultrasound transducers, probes, other external imaging devices, or other external devices, etc. The medical devices can also include medical imaging devices that provide or aid in the selection or generation of medical images for display. In some embodiments, the medical imaging device can be any device that is used to select a particular medical image for display or generate medical images. The medical imaging devices can include invasive medical devices, such as laparoscopic cameras or invasive ultrasound transducers, and non-invasive medical devices, such as external ultrasound transducers.

Depending on the medical device used, the medical device approach can be different. For example, each medical device can have unique dimensions, such as width, length, and/or thickness. Similarly, medical imaging devices can have different imaging depths, widths and/or thicknesses. In addition, medical imaging devices can use different scan frequencies, each of which can affect which tissue can be imaged. The system can use the various characteristics to determine the medical device approach.

In some embodiments, such as for invasive medical devices, the system can use the medical device's physical characteristics, such as its hardness or ability to pass through an object, deformability, curvature, length, width, thickness, and/or diameter to determine the medical device approach. Each invasive medical device can have its own physical characteristics that the system can use to determine the medical device approach. For example, the system can determine more medical device approaches for invasive medical devices that are longer, thinner, are more deformable, or have a smaller diameter. In some cases, the diameter, deformability, or thickness of the medical device can be different along its longitudinal axis. In such cases, the system can use the different thicknesses or deformability and location along the medical device axis to identify the medical device approaches.

With reference to FIG. 2, in some implementations, the system can eliminate paths 216 that pass through a region of bone 204, or other region through which the needle 218 is unable to pass. Similarly, the system can eliminate paths for the needle 218 that pass through a vital organ or a large blood vessel (not shown). In certain embodiments, the system can have information regarding the length of the needle 218, and can determine a maximum approach path length based at least in part on the length of the needle 218 and/or maximum reach of the needle 218. The system can exclude approach paths in which the distance from the approach region to the target structure 210 is longer than maximum approach length. In some embodiments, the system can include approach paths 216 that are wide and/or thick enough for the needle 218 to pass through, based on a known width and/or thickness of the needle 218.

In certain embodiments, such as for medical imaging devices, the system can use the imaging characteristics of the medical imaging device, such as, but not limited to, number of imaging sensors, number of transducer crystals, imaging frequency, imaging depth, resolution, fade, imaging width and/or imaging thickness to determine the medical device approach. In some cases, such as for invasive medical imaging devices, the system can also use the physical characteristics of the medical imaging device. In certain circumstances, the system can use the physical characteristics of a non-invasive medical imaging as well.

Similar to physical characteristics, each medical imaging device can have unique imaging characteristics that the system can use to determine the medical device approach. In certain embodiments, the system can determine more medical device approaches for medical imaging devices that have a larger imaging depth, larger imaging width, more imaging sensors, more transducer crystals, better resolution, less fade, or lower imaging frequency. For example, medical imaging devices with a larger imaging depth or width, more imaging sensors or more transducers can capture a larger image cross-section, which can enable the system to identify more potential paths. Similarly, the system can identify more medical device paths for medical imaging devices that have better resolution or fade less based on the distance from the imager, etc.

In addition, in some cases, imaging devices may unable to penetrate certain tissue depending on the frequency used. For example, many ultrasound transducers are unable to penetrate bone or gas and optical image sensors cannot penetrate tissue. Accordingly, the system can use the scan frequency or imaging type to identify medical device approaches. In addition, as described in greater detail above with reference to invasive medical devices, the physical characteristics of a medical imaging device can affect the number of medical device approaches identified by the system.

With continued reference to the embodiments illustrated in FIG. 2, the system can eliminate paths that pass through regions of gas 206 or bone 204 because the ultrasound probe 214 cannot penetrate the gas 206 or bone 204. The system 204 can use the imaging dimensions of the ultrasound probe to determine medical device paths 212 as well. For example, the ultrasound probe 214 can include a linear array of ultrasound crystals, each crystal configured for imaging along a path. The system can determine acceptable ultrasound scanning paths 212 where the unobstructed path has a 2D or 3D width of a threshold number of crystals.

In certain embodiments, the threshold number of crystals can be based on a number of crystals that have an unobstructed path to the target structure 210 and/or a number of crystals of the ultrasound probe 214. For example, the threshold number of crystals can be 25% or 50% of the total number of crystals of the ultrasound probe 214, and/or can be 1, 3, 5, 10, 15, or more crystals. In addition, the system can use the image depth of the ultrasound probe 214 determine the medical device approach paths 216. For example, the system can eliminate paths to the target structure 210 that are longer than the image depth of the ultrasound probe 210.

In some cases, the system can use a density threshold to identify the medical device approaches. As mentioned above, the density threshold can be based on the Hounsfield unit scale or similar scale, and can correspond to a minimum density, maximum density, or range of densities. In some embodiments, the system can identify objects and/or voxels that do not satisfy the density threshold (or are otherwise not to be used for a medical device approach) as obstructing objects. In certain embodiments, the system can exclude paths that intersect with obstructing objects. In addition, in some cases, the system can identify voxels or objects that have been annotated as not satisfying the density threshold or as obstructing objects.

In some embodiments, the density threshold can be static. For example, the system can identify objects having a density equal to or greater than bone as not satisfying the density threshold, irrespective of the medical device. In certain embodiments, such as when the density of critical tissue, such as heart tissue is known, the system can identify objects having the same density as the critical tissue as not satisfying the density threshold.

In certain embodiments, the density threshold can be based at least in part on a characteristic of the medical device. For example, gas within the image can satisfy the density threshold for a needle, but may not satisfy the threshold for an ultrasound device.

In some cases, the system can identify one or more semi-direct paths from the target structure 210 to the approach region. In certain embodiments, a semi-direct path may become available if a portion of the approach region or patient is deformed. For example, if a physician wants to access a portion of a patient under the rib cage, no direct path may be available. However, by compressing the abdomen or at a different time of the breathing cycling, a path may become available. Accordingly, in certain embodiments, the system can identify semi-direct medical device approaches based at least in part on a deformation of the approach region of an image. In some cases, the system can apply a flexibility factor to the approach region of the image. The flexibility factor can indicate a margin by which the approach region can be flexed. For example, the flexibility factor can indicate that the approach region can be flexed by 1-5 cm or by a percentage of the width or length of the image. Using the flexibility factor and other information as describe above, the system can identify one or more semi-direct medical device approaches.

Based on the identified medical device approaches the system can identify and display locations at the approach region for emplacing the medical device. In certain embodiments, the system can identify and display a particular emplacement for the medical device. For example, the system can highlight a region corresponding to the dimensions of the medical device. As another non-limiting example, based on two needle approach paths 216 determined to be acceptable, the system can display emplacements such as by displaying images of needles 218 along the acceptable paths 216, and/or by displaying highlighted or otherwise distinguishing portions of the approach region. Similarly, the system can display one or more ultrasound probe emplacements such as by displaying an image of an ultrasound probe 214, by displaying a scanning region or path 212, and/or by displaying a highlighted or otherwise distinguishable portion of the approach region.

In addition, in certain embodiments, the system can highlight the portions of the medical image area or volume that satisfy the density threshold and/or that can be used as part of a medical device approach. For example, the objects and/or voxels throughout the medical image area or volume that satisfy the density threshold can be highlighted, displayed in a particular color, or brought into focus. Similarly, the objects and/or voxels that do not satisfy the density threshold can be faded, taken out of focus, displayed in a different color etc.

In some embodiments, the system can track the location of a medical device and identify and display one or more medical device approaches based at least in part on the determined location of the medical device. The medical device approaches can be for the tracked medical device and/or for another medical device. For example, if the system is tracking a medical imaging device, it can display medical device approaches for the medical imaging device and/or for another medical device, such as an invasive medical device. In certain embodiments, the system can use the determined location of the medical device to display and/or highlight the medical device approaches that are nearest to the medical device. For example, if the system identifies six medical device approaches, it can use the determined location of the medical device to display or highlight the three medical device approaches that are closest to the determined location of the medical device.

Similar systems and methods can be applied with 3D volumetric images. FIG. 3 illustrates a 3D volumetric medical image 300 with exemplary image scanning and needle approach paths. The exemplary image 300 depicted in FIG. 3 includes a volume 302 containing a target structure 304, skin 306, bone 308, and other internal tissue 310. As described in greater detail with reference to FIG. 2, the system can determine approach paths, poses, and/or emplacements for medical devices such as an ultrasound probe 312 and a needle 314, or other medical device. In some aspects, acceptable, desirable, and/or suggested approach paths can be selected in a 3D volume based on the same or similar criteria as those discussed above with reference to FIG. 2. For example, ultrasound scanning paths can be selected so as to avoid regions of gas or bone 308 and/or based on imaging characteristics of the ultrasound probe 312. Needle approach paths can be selected so as to avoid regions of bone 308 or delicate structures, and/or based on the length of the needle 314.

Similar to the 2D system described with reference to FIG. 2, the system can use a variety of techniques to analyze and determine acceptable medical device approaches. For example, the system can utilize ray tracing, projective texture mapping, edge detection, one or more rendered images, etc., as described above by analyzing a plurality of direct or semi-direct paths between the approach region and the target structure 304. Some implementations can analyze the volume 302 along a plurality of spherical surfaces of increasing or decreasing radius, similar to the circular paths analyzed in 2D systems described above. Suggested emplacements 316 can then be displayed within the 3D volumetric medical image 300 for the reference of the physician.

When displaying 3D volumetric data, voxels in front (closer to the point-of-view location) can obscure the voxels behind them. In some instances, this can occlude information that can be important from preoperative 3D data. One way to address this is to allow the doctor to view the data as 2D slices 318, in cross section, etc., as described in greater detail in U.S application Ser. No. 14/166,179, entitled, SYSTEMS, METHODS, APPARATUSES, AND COMPUTER-READABLE MEDIA FOR IMAGE MANAGEMENT IN IMAGE-GUIDED MEDICAL PROCEDURES, incorporated by reference herein in its entirety. For example, a 2D slice 318 can be displayed based on a location of a medical device such as an ultrasound probe 312, with the location of the probe 312 determined based on data received from one or more emplacement sensors.

Moreover, the determined location of the probe 312 can be used to select suggested emplacements for a second medical device. For example, where the emplacement data indicates the location of an ultrasound probe 312 imaging the target structure 304, the guidance system can select one or more needle emplacements 316 near the location of the probe 312 (e.g., to facilitate the physician's simultaneous manipulation of the probe 312 and needle 314). In some embodiments, a previously obtained, real-time, or near real-time medical image (e.g., an ultrasound image obtained from the probe 312) can be superimposed on the 2D slice 318. In some embodiments, to enhance the visibility of the 2D slice 318, the 2D slice 318 can be displayed with increased brightness relative to the surrounding 3D volumetric image 300, or the surrounding 3D volumetric image 300 can be displayed with partial transparency or out of focus.

FIG. 4 is a flow diagram illustrative of an embodiment of a routine 400 implemented to display medical device emplacements. One skilled in the relevant art will appreciate that the elements outlined for routine 400 can be implemented by one or more computing devices/components that are associated with the systems described herein. Further, it will be understood that the various blocks described herein with reference to FIG. 4 can be implemented in a variety of orders. For example, some blocks can be implemented concurrently or in a different order as desired. For example, the system can perform blocks 420 and 430 concurrently and/or implement them in a different order.

At block 410, a volumetric medical image is received. As described elsewhere herein, the volumetric medical image can be obtained from any of various medical imaging technologies, including without limitation ultrasound, CT scan, MRI, open-magnet MRI, optical coherence tomography, PET scans, fluoroscopy, ultrasound, or other preoperative or intraoperative 2D or 3D anatomical imaging data. The volumetric medical image can be received as a single set of 3D volumetric data, or can be received as a plurality of 2D slices as described with reference to FIGS. 1A-B. In some embodiments, a volumetric medical image received as a single set of 3D volumetric data can be converted into a plurality of 2D image slices, and/or a volumetric medical image received as a plurality of 2D slices can be converted to a 3D volume as desired.

At block 420, the density of content within the volumetric medical image can be determined. As described in greater detail above, in some embodiments, the density of content can be determined based at least in part on an intensity value of voxels associated with the content within the volumetric medical image. For example, the density of content can be determined using a Hounsfield unit scale or other suitable scale for determining a mass density based on an image intensity.

At block 430, an indication can be received of a target location within the volumetric medical image. As described in greater detail above, in some embodiments, the indication can be received from a human user, such as a physician, can be received based on an input by the user, such as a keystroke or button press, or the like, and/or can be determined by the system, for example, based on a computer analysis of a region within the medical image, a detected reaction of a user, an amount of time a medical device is located at a particular emplacement, etc. In another example, the target location can be determined based on a real-time medical image. For example, as depicted in FIG. 3, the target location can be determined based on a structure being scanned by a user with an ultrasound probe. The target location can be determined based on the combination of the location of the target structure within the real-time ultrasound image and the determined emplacement of the emplacement sensor associated with the ultrasound probe. In various embodiments, one or more target locations can be selected and/or stored.

At block 440, the system can identify one or more obstructing objects within the volumetric medical image. In some embodiments, the system can identify the obstructing objects based at least in part on the determined density of content within the volumetric medical image, or otherwise identified as not to be used for a medical device approach. In certain embodiments, obstructing objects can be determined based on regions within the volumetric medical image having a density that does not satisfy a density threshold. As described previously, the density threshold can be a minimum density, maximum density or range of densities. For example, the system can identify a region having a density approximately equal to the density of bone as an obstructing object.

In some embodiments, the density threshold can be based at least in part on one or more imaging characteristics of a medical imaging device. For example, the density threshold can be based at least in part on a scan frequency of the medical imaging device. The maximum density of objects through which waves and/or radiation emitted by a medical imaging device can pass can vary based on the frequency of the waves and/or radiation (e.g., a scan frequency). Thus, the density threshold can be determined based on the known scan frequency of the medical imaging device. In another example, the density threshold can be determined based on the type of medical device (e.g., whether the device is an intrusive device, medical imaging device, or other type of medical device). In some aspects, the density threshold can include a single threshold, or can include a range of densities. For example, a density threshold for an ultrasound imaging device can include the range between −350 HU and 700 HU, so as to exclude regions of intestinal gas, air, and bone.

At block 450, one or more pathways can be determined from an approach region of the volumetric medical image to the target location. In some embodiments, the pathways can be identified based on pathways from the approach region of the medical image to the target that do not intersect or pass through an obstructing object. In certain embodiments, the system can identify the pathways based on pathways from the approach region of the medical image to the target that intersect or pass through at least two image slices. The pathways can be determined based on the methods described elsewhere herein, such as ray tracing, projective texture mapping, one or more rendered images, analysis of circular paths, analysis of spherical surfaces, or other methods.

As described in greater detail above, in some implementations, the one or more pathways can be determined based at least in part on characteristics of the medical device, such as threshold quantity of transducing elements at a particular emplacement of a medical imaging device each having a direct path to the target location that does not pass through the identified obstructing objects, other imaging characteristics of the medical device, and/or physical characteristics of the medical device. For example, for an ultrasound probe having a plurality of detecting crystals disposed in a linear array with known spacing, the plurality of pathways can be selected to be wide enough that at least 1, 3, 5, 10, 15, or more crystals of the ultrasound probe will have a direct path to the target location clear of obstructing objects, or a certain percentage of the ultrasound probe's crystals will have a direct path to the target location.

As described previously, in some cases, the system can identify the one or more pathways based on a tracked location of a medical device. In certain embodiments, the pathways identified can be for the tracked medical device and/or for another medical device.

At block 460, the system can cause a display to concurrently display the volumetric medical image and a plurality of emplacements on the approach region of the volumetric medical image for emplacements of one or more medical devices. Emplacements can be determined based at least in part on the determined plurality of direct pathways. For example, an emplacement for a medical imaging device can be determined as a location along the approach region of the volumetric medical image where the image scanning path of the medical imaging device includes one of the determined plurality of direct pathways within the volumetric medical image. In some embodiments, the plurality of emplacements can be displayed based at least in part on a determined emplacement of an emplacement sensor based on emplacement data received from the emplacement sensor. For example, the emplacement sensor can be associated with a medical device such as an ultrasound probe.

In some embodiments, the system described herein can be implemented in conjunction with and/or as part of a guidance system, as described below with reference to FIGS. 5A, 5B, and as described in greater detail in U.S. application Ser. No. 15/199,630, filed concurrently herewith, entitled, LOUPE DISPLAY.

FIG. 5A is a diagram illustrating an embodiment of an environment 500 for image-guided medical device approaches. In the illustrated embodiment, the environment 500 includes a display 502 displaying an image 550, an image guidance unit 504, a position sensing unit 506, a surgical system 508, imager 510, medical devices 512, 514, a patient 516, a stand 518, and a table 520. In some embodiments, an image guidance system 501 can include any one or any combination of the display 502, the image guidance unit 504, the position sensing unit 506, the surgical system 508, the imager 510, the medical devices 512, 514, the stand 518, and/or the table 520.

In some embodiments, the position sensing unit 506 can track medical devices 512, 514 within an area or volume, which can also be referred to as a tracked region or position sensing region, and provide data to the image guidance unit 504.

Although only two medical devices 512, 514 are shown in FIG. 5A, it will be understood that additional medical devices can be tracked and associated data can be provided to the image guidance unit 504. The image guidance unit 504 can process or combine the data and show image guidance data on display 502. This image guidance data can be used by a healthcare provider to guide a procedure and improve care. The image guidance data can also be used by the system to identify the medical device approaches described above.

There are numerous other possible embodiments of system 501. For example, many of the depicted components can be joined together to form a single component and can be implemented in a single computer or machine. Further, additional position sensing units can be used in conjunction with position sensing unit 506 to track relevant medical devices 512, 514, as discussed in more detail below. Additional imagers 510 can be included, and combined imaging data from the multiple imagers 510 can be processed by image guidance unit 504 and shown on display 502. Additionally, two or more surgical systems 508 can be used.

Information about and from multiple surgical systems 508 and attached medical devices 512 (and additional medical devices not shown) can be processed by image guidance unit 504 and shown on display 502. These and other possible embodiments are discussed in more detail below. It will be understood that any combination of the display objects, image guidance cues, etc., described herein can be displayed concurrently, or simultaneously. Further, reference to displaying objects “concurrently” and/or “simultaneously” is to be interpreted broadly and may refer to displaying objects in such a way that to a human observer the objects are visible at the same time.

Imager 510 can be communicatively coupled to image guidance unit 504. In some embodiments, imager 510 can be coupled to a second display unit (not shown). The second display unit can display imaging data from imager 510. The imaging data displayed on display 502 and displayed on second display unit can be the same or different. In some embodiments, the imager 510 can be an ultrasound machine 510, the medical device 514 can be a movable imaging unit, such as an ultrasound transducer 514 or ultrasound probe 514, and the second display unit can be a display associated with the ultrasound machine 510 that displays the ultrasound images from the ultrasound machine 510. In some embodiments, a movable imaging unit 514 can be communicatively coupled to image guidance unit 504. The movable imaging unit 514 can be useful for allowing a user to indicate what portions of a first set of imaging data are to be displayed. For example, the movable imaging unit 514 can be an ultrasound transducer 514, a needle or other medical device, for example, and can be used by a user to indicate what portions of imaging data, such as an intraoperative or preoperative CT scan, to show on a display 502 as image 550. The movable imaging unit 514 can also be used to identify medical device approaches for the moveable imaging unit 514 and/or for the medical device 512. Further, in some embodiments, there can be a third set of intraoperative or preoperative imaging data that can be displayed with the first set of imaging data.

In some embodiments, a navigation system 501 comprises a display 502 and a position sensing unit 506 communicatively coupled to image guidance unit 504. In some embodiments, position sensing unit 506, display 502, and image guidance unit 504 are coupled to the stand 518. Image guidance unit 504 can be used to produce images 550 that are displayed on display 502. The images 550 produced on display 502 by the image guidance unit 504 can be determined based on ultrasound or other visual images from the first medical device 512 and second medical device 514.

In the illustrated embodiment, the image 550 can include the volumetric medical image 300 described above in greater detail. In the image 550, some or all of the display objects can be displayed as 3D objects. Furthermore, the display objects in the image 550 can be displayed in a perspective based at least in part on a point-of-view location. More medical devices can be added to the system 501 as desired. For example, the system 501 can include an ultrasound probe, ablation needle, laparoscopic camera, stapler, cauterizer, scalpel and/or any other medical device or medical device, and the system 501 can determine a medical device approach for any one or more of the medical devices. The system 501 can also process and/or display collected data, such as preoperative CT scans, X-Rays, MRIs, laser scanned 3D surfaces etc.

In some embodiments, the imaging data obtained from one or both of medical devices 512 and 514 can include other modalities such as a CT scan, MRI, open-magnet MRI, optical coherence tomography (“OCT”), positron emission tomography (“PET”) scans, fluoroscopy, ultrasound, or other preoperative, or intraoperative 6D or 3D anatomical imaging data. In some embodiments, medical devices 512 and 514 can also be scalpels, implantable hardware, or any other device used in surgery. Any appropriate surgical system 508 or imager 510 can be communicatively coupled to the corresponding medical instruments 512 and 514.

The medical devices 512, 514 can be communicatively coupled to the position sensing unit 506 (non-limiting example: sensors embedded or coupled to the medical devices 512, 514 can be communicatively coupled with the position sensing unit 506). The position sensing unit 506 can be part of imager 510 or it can be separate. The position sensing unit 506 can be used to determine the emplacement of first medical device 512 and/or the second medical device 514. In some embodiments, the position sensing unit 506 can include a magnetic tracker and/or one or more magnetic coils can be coupled to medical devices 512 and/or 514. In some embodiments, the position sensing unit 506 can include an optical tracker and/or one or more visually-detectable fiducials can be coupled to medical devices 512 and/or 514. In some embodiments, the position sensing unit 506 can be located below the patient. In such embodiments, the position sensing unit 506 can be located on or below the table 520. For example, in embodiments where the position sensing unit 506 is a magnetic tracker, it can be mounted below the surgical table 520. Such an arrangement can be useful when the tracking volume of the position sensing unit 506 is dependent on the location of the position sensing unit 506, as with many magnetic trackers. In some embodiments, magnetic tracking coils can be mounted in or on the medical devices 512 and 514.

In some embodiments, the position sensing unit can determine one or more x, y, z coordinates and/or the quaternions (non-limiting examples: yaw, pitch, and/or roll) of tracking sensors associated with one or more of the medical devices 512, 514. In certain cases, the position sensing unit can determine the one or more x, y, z coordinates of the tracking sensors with respect to a position sensing coordinate system, as described in greater detail below. In some embodiments, the position sensing unit 506 can be an electromagnetic measurement system (non-limiting example: NDI Aurora system) using sensor coils for tracking sensors attached to the first and/or second medical devices 512, 514. In some embodiments, the position sensing unit 506 can be an optical 3D tracking system using fiducials for tracking sensors. Such optical 3D tracking systems can include the NDI Polaris Spectra, Vicra, Certus, PhaseSpace IMPULSE, Vicon MX, InterSense IS-900, NaturalPoint OptiTrack, Polhemus FastTrak, IsoTrak, or Claron MicronTracker2. In some embodiments, the position sensing unit 506 can each be an inertial 3D tracking system comprising a compass, accelerometer, tilt sensor, and/or gyro, such as the InterSense InertiaCube or the Nintendo Wii controller, mechanical tracking system, camera-based tracking system, radar-based tracking system, etc. In some embodiments, the position sensing unit 506 can be attached to or affixed on the corresponding medical device 512 and 514.

In some embodiments, the position sensing units 506, can include sensing devices such as the HiB all tracking system, a GPS device, or signal emitting device that would allow for tracking of the position and/or orientation (non-limiting example: emplacement) of the tracking sensor (also referred to as an emplacement sensor). In some embodiments, a position sensing unit 506 can be affixed to either or both of the medical devices 512, 514. The medical devices 512 or 514 can be tracked by the position sensing unit 506. A room coordinate system reference, such as the display 502 can also be tracked by the position sensing unit 506 in order to determine the emplacements of the medical devices 512, 514 with respect to the room coordinate system. Devices 512, 514 can also include or have coupled thereto one or more accelerometers, which can be used to estimate movement, position, and location of the devices. In some embodiments, the position sensing unit 506 can be an Ascension Flock of Birds, Nest of Birds, driveBAY, medSAFE, trakSTAR, miniBIRD, MotionSTAR, pciBIRD, or Calypso 6D Localization System and tracking sensors attached to the first and/or second medical devices 512, 514 can be magnetic tracking coils.

The term “tracking sensor” (also referred to as an emplacement sensor), as used herein, is a broad term encompassing its plain and ordinary meaning and includes without limitation all types of magnetic coils or other magnetic field sensing devices for use with magnetic trackers, fiducials or other optically detectable markers for use with optical trackers, such as those discussed above and below, or other sensors, such as accelerometers, gyroscopes, etc. In some embodiments, the tracking sensors can be implemented using optical position sensing devices, such as the HiBall tracking system and the position sensing unit 506 can form part of the HiBall tracking system. Tracking sensors can also include a GPS device or signal emitting device that allows for tracking of the position and/or orientation of the tracking sensor. In some embodiments, a signal emitting device might include a radio-frequency identifier (RFID). In such embodiments, the position sensing unit 506 can use the GPS coordinates of the tracking sensors or can, for example, triangulate the radio frequency signal being emitted by the RFID associated with tracking sensors. The tracking systems can also include one or more 3D mice.

In certain embodiments, the system 501 can register the location of the volumetric medical image 300 to the position sensing region and/or the patient 516. Accordingly, the system 501 can use the emplacement data and registered volumetric medical image 300 to identify the location of the medical devices 512, 514, relative to the volumetric medical image 300, as well as identify the emplacement of the medical devices 512, 514 relative to the identified medical device approaches.

Furthermore, the system 501 can use the emplacement data associated with the tracking sensors (non-limiting example: received from the tracking sensors or from the position sensing unit 506) to determine other emplacement information, including, but not limited to the emplacement of the medical device approaches as described above. In some cases, the tracking sensors can output the emplacement data, which can be used by the tracker to determine the emplacement of the tracking sensor. In certain cases, the tracker tracking the tracker sensors determines the emplacement of the tracking sensors without data being output from the tracking sensors.

In some embodiments, the display 502 displays 3D images to a user, such as a healthcare provider. Stereoscopic 3D displays separate the imagery shown to each of the user's eyes. This can be accomplished by a stereoscopic display, a lenticular auto-stereoscopic display, or any other appropriate type of display. The display 502 can be an alternating row or alternating column display. Example alternating row displays include the Miracube G240S, as well as Zalman Trimon Monitors. Alternating column displays include devices manufactured by Sharp, as well as many “auto-stereoscopic” displays (non-limiting example: Philips). In some embodiments, Sony Panasonic 3D passive displays and LG, Samsung, and/or Vizio 3D TVs can be used as well. Display 502 can also be a cathode ray tube. Cathode Ray Tube (CRT) based devices, can use temporal sequencing, showing imagery for the left and right eye in temporal sequential alternation. This method can also be used by projection-based devices, as well as by liquid crystal display (LCD) devices, light emitting diode (LED) devices, organic LED (OLED) devices, liquid crystal on silicon (LCOS) devices, DLP devices, virtual retinal display (MicroVision) devices, or the like.

In certain embodiments, the display 502 can be a head mounted display (HMD) worn by the user in order to receive 3D images from the image guidance unit 504. In such embodiments, a separate display, such as the pictured display 502, can be omitted. The 3D graphics can be produced using underlying data models, stored in the image guidance unit 504 and projected onto one or more 6D planes in order to create left and right eye images for a head mount, lenticular, or other 3D display.

The underlying 3D model can be updated based on the relative emplacements of the various devices 512 and 514, as determined by the position sensing unit(s) 506, and/or based on new data associated with the devices 512 and 514. For example, if the second medical device 514 is an ultrasound probe, then the underlying data model can be updated to reflect the most recent ultrasound image. If the first medical device 512 is an ablation needle, then the underlying model can be updated to reflect any changes related to the needle, such as power or duration information.

Any appropriate 3D graphics processing can be used for rendering including processing based on OpenGL, Direct3D, Java 3D, etc. Whole, partial, or modified 3D graphics packages can also be used, such packages including 3DS Max, SolidWorks, Maya, Form Z, Cybermotion 3D, VTK, Slicer, or any others. In some embodiments, various parts of the needed rendering can occur on traditional or specialized graphics hardware. The rendering can also occur on the general CPU, on programmable hardware, on a separate processor, be distributed over multiple processors, over multiple dedicated graphics cards, or using any other appropriate combination of hardware or technique.

One or more components, units, devices, or elements of various embodiments can be packaged and/or distributed as part of a kit. For example, in one embodiment, an ablation needle, one or more tracking sensors, 3D viewing glasses, and/or a portion of an ultrasound wand can form a kit. Other embodiments can have different elements or combinations of elements grouped and/or packaged together. Kits can be sold or distributed separately from or with the other portions of the system 501.

One will readily recognize that there are numerous other examples of image guidance systems 501 which can use, incorporate, support, or provide for the techniques, methods, processes, and systems described herein.

With continued reference to FIG. 5A, the display 502 shows a perspective view of the volumetric medical image 300, a virtual ultrasound probe 316, and a virtual needle 314. The virtual medical devices 314, 316 can be displayed in a virtual 3D scene with the display 502 acting as a window into the virtual 3D scene. Thus, as a medical device 512 is moved to the right with respect to a point-of-view location (non-limiting example: the location of the point-of-view for viewing the 3D space), the virtual medical device 558 can also move to the right. In some embodiments, the virtual medical devices 314, 316 can correspond to determined medical device emplacements for the medical devices 512, 514. For example, the virtual medical devices 314, 316 can indicate where the medical devices 512, 514 are to be emplaced. In such embodiments, the display 502 can include additional virtual medical devices indicating the determined location of the medical devices 512, 514 relative to the recommended emplacements. Additional cues can be displayed to aid the user in emplacing the medical devices in the recommended emplacements.

In some embodiments, if the medical device 512 is rotated 90° so that the tip of the medical device is pointing away from the point-of-view location (non-limiting example: at the display 502), the virtual medical device 558 will likewise show the change in orientation, and show the tip of the virtual medical device 558 in the background and the other end of the virtual medical device 558 in the foreground. In some embodiments, as described in greater detail in U.S. application Ser. No. 14/212,933, incorporated herein by reference in its entirety, the point-of-view location can be a fixed location, such as a predetermined distance/angle from the display 502 or stand 518 and or a location configured by the user; or the point-of-view location can by dynamic. For example, the system 501 can track a user in real-time and determine the point-of-view location based at least in part on the tracked location of the user.

Other embodiments can track and display other types of instruments and their features. For example, a healthcare provider may want to track one or more of a scalpel, a biopsy, a cauterizer (including an electrocauterizer and Bovies), forceps, cutting loops on hysteroscopes, harmonic shears, lasers (including CO₂ lasers), etc. For example, in various embodiments, the following devices can be tracked and various aspects of their design displayed on display 502: Olympus™ OES Pro Hystero-Resectoscope, SonoSurg Ultrasonic Surgical System Olympus™ GF-UC 560 Endoscope Wallus™ Embryo Transfer Catheter AngioDynamics®, NanoKnife™, VenaCure™ laser, StarBurst, Uniblade, Habib®, Resector Bovie™ Electrodes, Covidien Evident™, Cool-tip™ Ablation Antennas, Opti4™ Electrodes Microsulis MEA (microwave endometrial ablation), Acculis Halt™ Medical System Optimed BigLumen Aspiration Catheter Optimed Optipure Stent Central venous catheterization introducer medical device (such as those made by Bard and Arrow).

Once tracked, a healthcare provider is able to see image guidance data on display 502 that will allow her to know the relative pose, location, or emplacement of the tracked instrument(s) with respect to one another or with respect to imaging data and will be able to see, on display 620, the features of the instrument rendered in the scene.

Referring now to FIG. 5B, virtual image content may be displayed on a head mounted display (HMD) 650 instead of or in addition to a display 502 as depicted in FIG. 5A. The HMD 650 may include one or more stereoscopic displays 652, 654 configured to display 3D content to a wearer of the HMD 650. For example, the HMD 650 can include a left stereoscopic display 652 configured to project visual content 653 to a left eye of a wearer, and a right stereoscopic display 654 configured to display visual content 655 to a right eye of a wearer. In some embodiments, displays 652, 654 can be opaque, and can be sized and located so as to occupy a subset of the field of view of a wearer. In certain embodiments, the displays 652, 654 can be transparent or translucent, or can be implemented as retinal scan displays that project an image onto the eye rather than display an image on the display screen.

Displays 652, 654 can allow the displayed content 653, 655 to be seen clearly without glare or interference due to light from the world in the region beyond the displays 652, 654. In certain embodiments, displays 652, 654 occupying less than the entire field of view of the wearer can allow the wearer to view the virtual content 653, 655 while also viewing the real environment in the portion of the wearer's field of view unoccupied by displays 652, 654, such as through transparent portions 656, 658 of the HMD 650.

In some embodiments, the imaging systems described herein can display virtual image content on the displays 652, 654 using a location offset with respect to the location of corresponding objects. For example, rather than displaying and/or augmenting content that is directly in front of the displays 652, 654 and/or the HMD 650, the displays 652, 654 can display and/or augment objects that are located elsewhere, such as below, above, or to the side of the displays 652, 654 and/or the HMD 650. In the illustrated embodiment, the virtual medical devices 314, 316 can be displayed with a vertical offset relative to the medical devices 512, 514 so as to allow a wearer of the HMD 650, such as a surgeon, to simultaneously view the virtual medical devices 558, 560 on the displays 652, 654 and the patient 516 with real medical devices 512, 514 located below the HMD 650.

The offset can be predetermined based on a dimension or preference of an individual wearer prior to use, or based on a default such as an average height or dimension of an expected wearer, or dynamic based on data received during use. An example offset can be a distance equal or approximately equal to the vertical distance between a wearer's elbow and the wearer's eye (non-limiting example: in the range of 0.5 m to 5 m), a measured distance between the HMD 650 and the medical devices 512, 514, etc. Additional details regarding the offset are described in U.S. application. Ser. No. 15/199,630, filed concurrently herewith, entitled, LOUPE DISPLAY.

The HMD 650 can be implemented with any of the imaging systems described with reference to FIG. 5A. For example, displays 652, 654 can display virtual medical devices 558, 560 corresponding to real medical devices 512, 514. Displays 652, 654 can further display any other virtual image features described elsewhere herein, such as a medical device approach.

The processes, computer readable medium, and systems described herein can be performed on various types of hardware, such as computer systems or computing devices. In some embodiments, position sensing units, a display unit, image guidance units, and/or any other module or unit of embodiments herein can each be separate computing devices, applications, or processes or can run as part of the same computing devices, applications, or processes—or one of more can be combined to run as part of one application or process—and/or each or one or more can be part of or run on a computing device. Computing devices or computer systems can include a bus or other communication mechanism for communicating information, and a processor coupled with the bus for processing information. A computer system or device can have a main memory, such as a random access memory or other dynamic storage device, coupled to the bus. The main memory can be used to store instructions and temporary variables. The computer system or device can also include a read-only memory or other static storage device coupled to the bus for storing static information and instructions. The computer systems or devices can also be coupled to a display, such as a CRT, LCD monitor, LED array, e-paper, projector, or stereoscopic display. Input devices can also be coupled to the computer system or device. These input devices can include a mouse, a trackball, touchscreen, tablet, foot pedal, or cursor direction keys.

Each computer system or computing device can be implemented using one or more physical computers, processors, embedded devices, field programmable gate arrays (FPGAs), or computer systems or portions thereof. The instructions executed by the computer system or computing device can also be read from a computer-readable medium. The computer-readable medium can be non-transitory, such as a CD, DVD, optical or magnetic disk, laserdisc, flash memory, or any other medium that is readable by the computer system or device. In some embodiments, hardwired circuitry can be used in place of or in combination with software instructions executed by the processor. Communication among modules, systems, devices, and elements can be over a direct or switched connections, and wired or wireless networks or connections, via directly connected wires, or any other appropriate communication mechanism. Transmission of information can be performed on the hardware layer using any appropriate system, device, or protocol, including those related to or utilizing Firewire, PCI, PCI express, CardBus, USB, CAN, SCSI, IDA, RS232, RS422, RS485, 802.11, etc. The communication among modules, systems, devices, and elements can include handshaking, notifications, coordination, encapsulation, encryption, headers, such as routing or error detecting headers, or any other appropriate communication protocol or attribute. Communication can also messages related to HTTP, HTTPS, FTP, TCP, IP, ebMS OASIS/ebXML, DICOM, DICOS, secure sockets, VPN, encrypted or unencrypted pipes, MIME, SMTP, MIME Multipart/Related Content-type, SQL, etc.

Any appropriate 3D graphics processing can be used for displaying or rendering, including processing based on OpenGL, Direct3D, Java 3D, etc. Whole, partial, or modified 3D graphics packages can also be used, such packages including 3DS Max, SolidWorks, Maya, Form Z, Cybermotion 3D, VTK, Slicer, or any others. In some embodiments, various parts of the needed rendering can occur on traditional or specialized graphics hardware. The rendering can also occur on the general CPU, on programmable hardware, on a separate processor, be distributed over multiple processors, over multiple dedicated graphics cards, or using any other appropriate combination of hardware or technique.

As will be apparent, the features and attributes of the specific embodiments disclosed above can be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure.

Conditional language used herein, such as, among others, “can,” “could,” “might,” “can,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment.

Any process descriptions, elements, or blocks in the processes, methods, and flow diagrams described herein and/or depicted in the attached figures should be understood as potentially representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process. Alternate implementations are included within the scope of the embodiments described herein in which elements or functions can be deleted, executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those skilled in the art.

All of the methods and processes described above can be embodied in, and fully automated via, software code modules executed by one or more general purpose computers or processors, such as those computer systems described above. The code modules can be stored in any type of computer-readable medium or other computer storage device. Some or all of the methods can alternatively be embodied in specialized computer hardware.

It should be emphasized that many variations and modifications can be made to the above-described embodiments, the elements of which are to be understood as being among other acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims. 

What is claimed is:
 1. A method of medical device guidance, the method comprising: obtaining a volumetric medical image, the volumetric medical image including a plurality of image slices; identifying a target location within the volumetric medical image; determining a density of content within the volumetric medical image based at least in part on intensity values of voxels associated with the content within the volumetric medical image; identifying a first direct pathway to the target location that does not pass through regions of the volumetric medical image that satisfy a first density threshold; determining a suggested pose of a medical imaging device based at least in part on the first direct pathway, wherein when the medical imaging device is placed at the suggested pose, a scan path of the medical imaging device at least partially overlaps with the first direct pathway; identifying a second direct pathway to the target location that does not pass through regions of the volumetric medical image that satisfy a second density threshold, wherein the regions that satisfy the second density threshold correspond to areas of the volumetric medical image that include an obstructing object, and wherein the second direct pathway corresponds to a potential entry point into tissue of a patient; determining a suggested pose of a medical device based at least in part on the second direct pathway; and causing a display to concurrently display: at least part of the volumetric medical image, an indication of the suggested pose for the medical imaging device, and an indication of the suggested pose for the medical device.
 2. The method of claim 1, wherein the second direct pathway passes through at least two of the plurality of image slices.
 3. The method of claim 1, wherein said identifying the target location within the volumetric medical image comprises: receiving an indication of the target location within the volumetric medical image; and determining the target location within the volumetric medical image based at least in part on the received indication.
 4. The method of claim 1, wherein said identifying the target location within the volumetric medical image is based at least in part on an amount of time that the medical device is located at a particular location.
 5. The method of claim 1, further comprising: wherein the second density threshold is based at least in part on one or more characteristics of the medical imaging device, wherein the one or more characteristics of the medical imaging device comprises one or more of a number of imaging sensors of the medical imaging device, a number of transducer crystals of the medical imaging device, an imaging depth of the medical imaging device, a resolution of the medical imaging device, a fade of the medical imaging device, an imaging width of the medical imaging device, an imaging thickness of the medical imaging device, a scan frequency of the medical imaging device, or a type of the medical imaging device.
 6. The method of claim 1, wherein said identifying the first direct pathways is based at least in part on a scan depth of the medical imaging device.
 7. The method of claim 1, wherein said identifying the second direct pathway comprises: capturing a volume of voxels between the target location and an entry point; mapping the volume of voxels to an image area; and identifying at least a portion of the image area in which an approach region is visible.
 8. The method of claim 1, wherein the regions that satisfy the first density threshold correspond to areas of the volumetric medical image that include a gas.
 9. The method of claim 1, wherein the regions that satisfy the first density threshold correspond to areas of the volumetric medical image that include a bone.
 10. A non-transitory computer-readable storage medium storing computer-executable instructions that when executed by one or more processors cause the one or more processors to: obtain a volumetric medical image, the volumetric medical image including a plurality of image slices; identify a target location within the volumetric medical image; determining a density of content within the volumetric medical image based at least in part on intensity values of voxels associated with the content within the volumetric medical image; identify a first direct pathway to the target location that does not pass through regions of the volumetric medical image that satisfy a first density threshold; determine a suggested pose of a medical imaging device based at least in part on the first direct pathway, wherein when the medical imaging device is placed at the suggested pose a scan path of the medical imaging device at least partially overlaps with the first direct pathway; determine a second direct pathways to the target location that does not pass through regions of the volumetric medical image that satisfy a second density threshold, wherein the regions that satisfy the second density threshold correspond to areas of the volumetric medical image that include an obstructing object; determine a suggested pose of a medical device based at least in part on the second direct pathway; and cause a display to concurrently display: at least part of the volumetric medical image, an indication of the suggested pose of the medical imaging device, and an indication of suggested pose of the medical device.
 11. The non-transitory computer-readable storage medium of claim 10, wherein each of the first and second direct pathways passes through at least two of the plurality of image slices.
 12. The non-transitory computer-readable storage medium of claim 10, wherein to identify the target location within the volumetric medical image, the computer-executable instructions further cause the one or more processors to: receive an indication of the target location within the volumetric medical image; and determine the target location within the volumetric medical image based at least in part on the received indication.
 13. The non-transitory computer-readable storage medium of claim 10, wherein to identify the target location, the computer executable instructions cause the one or more processors to identify the target location within the volumetric medical image based at least in part on an amount of time that the medical device is located at a particular location.
 14. The non-transitory computer-readable storage medium of claim 10, wherein the first density threshold is based at least in part on one or more characteristics of the medical imaging device, wherein the one or more characteristics of the medical imaging device comprises one or more of a number of imaging sensors of the medical imaging device, a number of transducer crystals of the medical imaging device, an imaging depth of the medical imaging device, a resolution of the medical imaging device, a fade of the medical imaging device, an imaging width of the medical imaging device, an imaging thickness of the medical imaging device, a scan frequency of the medical imaging device, or a type of the medical imaging device.
 15. The non-transitory computer-readable storage medium of claim 10, wherein the regions that satisfy the first density threshold correspond to areas of the volumetric medical image that include at least one of a gas or a bone.
 16. A system for medical device guidance, comprising: a display; and one or more processors configured to: obtain a volumetric medical image, the volumetric medical image including a plurality of image slices; identify a target location within the volumetric medical image; determine a suggested pose for a medical imaging device based at least in part on the volumetric medical image; identify a direct pathways to the target location that does not pass through regions of the volumetric medical image that satisfy a density threshold, wherein the density threshold corresponds to intensity values of voxels associated with content within the volumetric medical image, and wherein the regions that satisfy the density threshold correspond to areas of the volumetric medical image that include an obstructing object; determine a suggested pose for a medical device based at least in part on the identified direct pathway; and cause the display to concurrently display: at least part of the volumetric medical image, an indication of the suggested pose for a medical imaging device, and an indication of the suggested pose for the medical device.
 17. The system of claim 16, wherein the one or more processors are further configured to identify a second direct pathway to the target location that does not pass through regions of the volumetric medical image that satisfy second density threshold, wherein to determine the suggested pose of the medical imaging device is based at least in part on the second direct pathway.
 18. The system of claim 17, wherein when the medical imaging device is placed at the suggested pose a scan path of the medical imaging device at least partially overlaps with the second direct pathway.
 19. The system of claim 17, wherein the regions that satisfy the second density threshold correspond to areas of the volumetric medical image that include a gas.
 20. The system of claim 17, wherein the regions that satisfy the second density threshold correspond to areas of the volumetric medical image that include a bone. 